1. Field of the Invention
This invention relates to a vehicle environment monitoring system that monitors an environment of an automotive vehicle on which the vehicle is installed. The system detects an object which may collide with the vehicle from an image obtained by an imaging device mounted on the vehicle, thereby avoiding collision against large animals, such as a deer, a bear and the like, since such collision has an adverse influence on the running of the vehicle.
2. Description of the Prior Art
Conventionally, a detection system for detecting an object crossing a road ahead of a vehicle was proposed in Japanese Laid-Open Patent Publication (Kokai) No. 9-226490, the proposed system detects a distance between the vehicle and the object based on the displacement between images of the object, that is, the parallax of images obtained by two CCD (charge-coupled device) cameras mounted on the vehicle, thereby detecting a pedestrian 30 to 60 meters ahead of the vehicle.
However, the above conventional apparatus determines the possibility of collision against an object by using the direction of an optical flow of the object detected based on images of the object obtained by the cameras, without further processing, which results in degraded determining accuracy depending on a relative distance between the vehicle and the object, and the speed of the vehicle. That is, when a vehicle speed is much higher than the speed of a moving object, an optical flow on the image, which corresponds e.g. to an object actually moving toward the center of a road, is sometimes tracked as a vector extending outside the road, which causes an erroneous determination of the possibility of potential collision.